Better way to import `declarative_base` from SQLAlchemy.

Import `declarative_base` in a way that is compatible with any
SQLAlchemy version between 1.3 and 2.x.

platypush/backend/covid19/__init__.py

@@ -3,9 +3,10 @@ import os
 from typing import Optional, Union, List, Dict, Any
 
 from sqlalchemy import create_engine, Column, Integer, String, DateTime
-from sqlalchemy.orm import sessionmaker, scoped_session, declarative_base
+from sqlalchemy.orm import sessionmaker, scoped_session
 
 from platypush.backend import Backend
+from platypush.common.db import declarative_base
 from platypush.config import Config
 from platypush.context import get_plugin
 from platypush.message.event.covid19 import Covid19UpdateEvent

platypush/backend/github/__init__.py

@@ -6,9 +6,10 @@ from typing import Optional, List
 
 import requests
 from sqlalchemy import create_engine, Column, String, DateTime
-from sqlalchemy.orm import sessionmaker, scoped_session, declarative_base
+from sqlalchemy.orm import sessionmaker, scoped_session
 
 from platypush.backend import Backend
+from platypush.common.db import declarative_base
 from platypush.config import Config
 from platypush.message.event.github import (
     GithubPushEvent,

platypush/backend/http/request/rss/__init__.py

@@ -12,10 +12,11 @@ from sqlalchemy import (
     ForeignKey,
 )
 
-from sqlalchemy.orm import sessionmaker, scoped_session, declarative_base
+from sqlalchemy.orm import sessionmaker, scoped_session
 from sqlalchemy.sql.expression import func
 
 from platypush.backend.http.request import HttpRequest
+from platypush.common.db import declarative_base
 from platypush.config import Config
 from platypush.context import get_plugin
 from platypush.message.event.http.rss import NewFeedEvent

platypush/backend/mail/__init__.py

@@ -9,9 +9,10 @@ from threading import Thread, RLock
 from typing import List, Dict, Any, Optional, Tuple
 
 from sqlalchemy import engine, create_engine, Column, Integer, String, DateTime
-from sqlalchemy.orm import sessionmaker, scoped_session, declarative_base
+from sqlalchemy.orm import sessionmaker, scoped_session
 
 from platypush.backend import Backend
+from platypush.common.db import declarative_base
 from platypush.config import Config
 from platypush.context import get_plugin
 from platypush.message.event.mail import (
@@ -40,6 +41,7 @@ class MailboxStatus(Base):
 
 # </editor-fold>
 
+
 # <editor-fold desc="Mailbox model">
 @dataclass
 class Mailbox:

platypush/common/db.py

@@ -1,3 +1,10 @@
-from sqlalchemy.orm import declarative_base
+from sqlalchemy import __version__
+
+sa_version = tuple(map(int, __version__.split('.')))
+
+if sa_version >= (1, 4, 0):
+    from sqlalchemy.orm import declarative_base
+else:
+    from sqlalchemy.ext.declarative import declarative_base
 
 Base = declarative_base()

platypush/plugins/media/search/local.py

@@ -12,9 +12,10 @@ from sqlalchemy import (
     PrimaryKeyConstraint,
     ForeignKey,
 )
-from sqlalchemy.orm import sessionmaker, scoped_session, declarative_base
+from sqlalchemy.orm import sessionmaker, scoped_session
 from sqlalchemy.sql.expression import func
 
+from platypush.common.db import declarative_base
 from platypush.config import Config
 from platypush.plugins.media import MediaPlugin
 from platypush.plugins.media.search import MediaSearcher